3, 6-diisopropyl catechol antioxidant



1 process.

3,6-D1ISOPROPYL CATECHOL ANTIOXIDANT George G. Ecke, Fernrlaie, and Alfred J.

ham, Mich., assignors to Ethyl Corporation, New York,

This'invention relates to a novel class of chemical cornw P tsfi o 2,83 1,817 Patented Apr. 22, 1958 2 sealed and pressurized with propylene and heated to 265 C. The temperature was maintained between 265 and 275.5 C. while the pressure varied from 500 to 700 p. s. i. g. over a 3 hour and 40 minute period. The vessel Kolka, Birmin gpounds and to compositions of matter containing these compounds as antioxidants.

It has been discovered that a heretofore. unknown class of diisopropyl catechols possesses outstanding antioxidant properties in a, wide variety of organic materials which are subject to oxidative deterioration. f

percent hydrogen.

. It is an object of this invention to provide a novel class of chemicals possessing outstanding antioxidant characteristics. Another object is to provide a class of diisopropyl catechols having outstanding antioxidantproperties. A further object is torprovide novel compositions I ofzmatter containing a diisopropyl catechol as anoxidation inhibitor. H I I 1 The objects of this inventio-nare accomplishedby a diisopropyl catechol having-at least one isopropylgroup ortho toa hydroxyl group andpa second isopropyl group was then cooled and the contents'were discharged into a distillation apparatus and the volatile components of the reaction mass were flashed ofi at reduced pressure leaving 134 parts of residue. The 621.5 parts of volatile components were collected and charged to a 3 foot helix packed column and rectified at reduced pressure.

Three main cuts plus a small amount of recovered catechol and some unidentified ether were retained as products of the rectification. The first main cut consisted of 7 3.9 parts of 1,2-dihydroxy-3-isopropylbenzene (3-isopropyl catechol). Analysis of this compound showed that it contained 71.3 percent carbon and 7.92

Infrared analysis indicated the hydroxyl 'bond to be resolved into two free hydroxyls with different degrees of'hindrance, and further indicated that the substitution type was 1,2,3.

The second main cut of 350.1 parts was identified as 3,6-diisopropylcatechol, boiling at'172 to 173.5 C. at

30 millimeters of mercury. This material was recrystalin a position otherthan the four-position. Thus, the f novel compounds of this invention have-the formulai The novel diisopropyl catechols of this invention are efiective antioxidants when included small amounts in organic material tending to deteriorate in the presence of air or oxygen. Thus, such materials as petroleum products, vegetable and animal fats, natural and synthetic rubber and other polymeric organic material are protected by the inclusion of one ofthe novel diisopropyl catechols of this invention.

The compounds of this invention are crystalline solids whichare soluble in liquid hydrocarbons such as benzene, isooctane, gasoline, lubricating oil and the like.

i The novel diisopropyl catechols are prepared by the a The following example in "which' all parts are by weight illustrates the" preparation and isolation of the compounds' of this: invention. It should be notedthat' the aluminum isopropoxidejreacts with catechol to form the catalyst aluminum catecholate in theinitial stage of the EXAMPLEI A pressure resistant vessel having a removable cap fo r charging and discharging liquids and solids, and which was equipped with a plurality of gasinlet and outlet lines,

temperature measuring devices, pressure gauges and a mechanical agitator .was flushed, with mtrogen ,and

ing at from 74 to 75 C. Analysis of this compound showed that it -contained 74.3 percent carbon and 9.34 percent hydrogen. The infrared spectrum was that of a tetra substituted benzene nucleus :in which the substituents werelonconsecutively adjacent carbon atoms.

The third main cut consisted of 106.2 parts of 3,5-diiso propyl catechol, a solid which boiled at 179 to 181 C. at 30 millimeters pressure. When this compound was re crystallized from isooctane a crystalline solid melting at 91.5 C. resulted. Analysis of this compound indicated that it contained 74.0 percent carbon and 9.07 percent hydrogen. The infrared spectrum was that of a tetra substituted benzene nucleus having two free hydroxyls with different degrees of hindrance, in which the substituents were not on adjacent carbon atoms.

The diisopropyl catechols of this invention are excellent antioxidants when dissolved in liquid hydrocarbon fuels containing olefinic organic constituents. In particular, outstanding results are achieved when 3,6-diisopropyl catechol is added to gasoline tending to deteriorate in the presence of air. 7

To demonstrate the superiority as antioxidants of the novel diisopropyl catechols prepared by the process of thisinvention comparative tests were conducted using a representative unsaturated hydrocarbon, 2,4,4-trimethylpentene-l, which is found inmany cracked gasolines. Each of these novel diisopropyl catechols was tested for antioxidant activity in the hydrocarbon in a concentration of 4 milligrams of antioxidant per 100 milliliters of fuel. For comparative purposes, another portion of the same hydrocarbon containing an identical concentration of 4- methyl-2,6-di-tert-butyl phenol was also tested. The test procedure: was the standard method of the American Society for Testing Materials for the determination of the charged with 440.4 partsof catechol, 272 parts of toluene and-.34 parts of aluminum isopropoxide. The yessel was oxidation stability of gasoline (Induction Period Method) ASTM Designation: D-525- 46, as fully described in Part III-A, ASTM Standards for 1946. According to this method, the induction period is the period during which there is no drop in pressure indicating no absorption of oxygen, whenthe test material is placed in a test bomb maintained at a temperature of C. with an initial pressure of 100 pounds per square inch gauge of oxygen. Comparative ratings'were established by dividing the inductionperiod of each antioxidant-containing sample by the induction period of a sample of 2,4,4-trimethylpentene-l, which contained no added antioxidant. The results of these tests are summarized in Table I.

.3 Table l ANTIOXIDAN'I ACTIVITY OF DIISOPROPYL OAIEOHOLS Induo- T Antioxidant tion Rating Period,

Minutes None 95 1.0 3,6-Diisopropyl OateehoL- 1,440+ ;15.'5+ 3,5-Diisopropyl Oatechol 1, 440+ 15.-+ 4-Methyl-2,(i-di-tert-butyl phenol 40.; 4.4

The above data show that the novel derivatives of catechol are far superior as antioxidants when compared to 4-methyl-2,6-di-tert-butyl phenol, which'is a standard, widely used commercial antioxidant. It should be pointed out that in the case of both the 3,5- and 3,6-diisopropyl catechol the tests were discontinued after 1440 -rninutes, at which time there was no, evidence' of,any decrease in the oxygen pressure. The true ratings for these compounds are, therefore, greater than those indicated in TablcI. V I

The following examples, in which all p'artsare by weight, are illustrative specific examples of the use of the novel compounds of this invention in organic "mate.- rial normally tending to deterioratein the presence of air.

EXAMPLE II EXAMPLE III To 1000 parts of a gasolinehaving 44.0 percent paraffins, 17.9 percent olefins and 38.1 percent aromatics, an initial evaporation temperature of 94 F. and'a final evaporation temperature of 119 F. is added parts of 3,6-diisopropyl catechol. The mixture is agitatedto dissolve the 3,6-diisopropyl catechol. The'resulting'fuel has an excellent stability to oxidative deterioration.

EXAMPLE I To 5000 parts of'a liquid hydrocarbon fuel*having'49.7 percent paraffius, 22.3 percent olefins and 28.0 percent aromatics, an initial evaporation temperature of 81 F. and a final evaporation temperature of 410 F. is added parts of an equal molar mixture of 3,5- and 3,6-diisopropyl catechol. The fuel is agitated to dissolve the mixture. The resulting fuel is stable to oxidative deterioration.

EXAMPLE V To 1000 gallons of the fuel described in Example IV is added 3000 milliliters of tetraethyllead, 0.5 theory bromine as ethylene dibromide, 1.0 theory of chlorine as ethylene dichloride and 9 grams of 3,5-diisopropyl cate- 4 agitated until a homogeneous oxygen stable the ingredients is achieved.

EXAMPLE VIII To an antiknock fluid composition which is to be used as an additive to gasoline and which contains 61.5 parts of tetraethyllead, 17.9 parts of ethylene dibromide and 18.8 parts of ethylene dichloride is added with agitation 1.3 parts of 3,6-diisopropyl catechol. The resulting composition is stable for long periods when exposed to air.

EXAMPLE IX EXAMPLE X To 1000 parts of polyethyleneproduced by oxygen catalyzed reaction under a'pressure of 20,000 atmospheres and having an average molecular weight of "40,000 is added and mixed 5 parts of 3,5-diisopropyl catechol as an antioxidant.

The above examples illustrate compositions of this invention which possess greatly enhanced resistance to oxidasolution of tive deterioration by virtue of the presence therein of a chcl. The mixture is agitated until a homogeneous oxygen stable solution of all the ingredients is achieved.

EXAMPL v To 1000 parts of a commercially available diesel fuel having a cetane number of 51.7 and a 50 percent evaporation temperature of 509 F. is added 3 parts of 3,6-diisopropyl catechol. The resulting fuel in stable to oxidative deterioration.

EXAMPLE VII diisopropyl catechol of this invention.

' The novel diisopropyl catechols find important utility as antioxidants in a wide variety of other'oxygen sensitive materials. Thus, the addition of small quantitiesof this compound to such materials as turbine, hydraulic, transformer and other highly refined industrial oils; waxes; soaps and greases; plastics; organo-metallic compositions such as tetraethyllead and tetraethyllead antiknock fluids; elastomers including natural rubber; crankcase lubricating oils; and the like, greatly increases their resistance to deterioration in the presence of oxygen, air, or ozone. The compounds of this invention are also very effective antioxidants for high molecular weight hydrocarbon polymers, such as polyethylene, polystyrene, polyisobutylene, polybutadiene, isobutylene-styrene copolymers, methyl rubber, polybutene rubber, natural rubber, butyl rubber, GR-S rubber, GR-N rubber, piperylene rubber, di nethyl butadiene rubber and the like. For this purpose 3,5- diisopropyl catechol is preferred because of its higher melting point. I g

The diisopropyl catechols of this invention are als'o usefulin protecting petroleum waxparafiiu wax and micro-crystalline Waxagainst oxidative deterioration. The compounds of this invention also find use in the stabilization of edible fats and oils ofanimal orvegetable origin which tend to become rancid especially during long periods of storage because of oxidative deterioration. Typical representatives of these edible fats and oils are linseed oil, cod liver oil, castor oil, soybean oil, rapeseed oil, coconut oil, olive oil, palm oil, corn oil, sesame oil, 'peanut oil, babassu oil, butter, fat, lard, beef tallow, and

the like; g 1

Thefollowing examples illustrate typical edible-com- .positions protected by a diisopropyl catechol of this invention,

EXAMPLE xi Two parts of 3,6-diisopr0pyl catechol are blended with 10,000 parts of lard. The resulting protected lard is stable over long storage periods in contradistinction to the unprotected product.

, EXAMPLEXII I h To 5,000 parts of olive oil is added 1 part 3,5-diiso- =propyl catechol and the mixture is agitated to produce a homogeneous blend which is stable to oxidative deteriorationfor'a'1ong period. j l

The amounts of diisopropyl catechol employed are dependent upon the nature of the material to be protected and the conditions to be encountered. Generally speaking, amounts in the order of about 0.001 to about 2 percent by weight of the material to be protected can be used. However, in most instances where the material to be protected does not have an unusual oxidative instability amounts from about 0.01 to about 1 percent are satisfactory. i

We claim:

1. 3,6-diisopropyl catechol.

2. As a new composition of matter an organic material normally tending to deteriorate in the presence of air containing as an antioxidant a small amount of the compound of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS Stoes ser et al Nov. 21, 1939 Stevens July 15, 1952 OTHER REFERENCES 

1. 3,6-DIISOPROPYL CATECHOL.
 2. AS A NEW COMPOSITION OF MATTER AN ORGANIC MATERIAL NORMALLY TENDING TO DETERIORATE IN THE PRESENCE OF AIR CONTAINING AS AN ANTIOXIDANT A SMALL AMOUNT OF THE COMPOUND OF CLAIM
 1. 